1. Field of the Invention
This invention relates to a novel thiophene derivative polymer and a thiophene derivative polymer composition obtained by doping the polymer with an anion. The polymer composition exhibits electric properties which make it suitable as a semiconductor. Further, the polymer composition and the polymer possess special colors.
2. Prior Art Statement
In recent years, display devices have come to play an important role as input and output means. The most widely used type of display device uses a video tube. Such tubes, however, have a disadvantage in that they have large size and weight and consume much electric power. As a consequence, liquid crystal displays and electrochromic displays have been studied and developed to take the place of video tubes.
In parallel with this electronic technology is being incorporated in many kinds of equipment. As a result, such equipment can be reduced in size and improved in performance. The success in the incorporation of electronic technology is ascribable in a great measure to the development of semiconductors, integrated circuits, and LSI's. Display materials and electronic materials are expected to find expanding applications and demand for such materials is expected to grow in the future. Thus the development of new semiconductor materials is important and studies are being continued on both organic and inorganic materials. Macromolecular semiconductors are therefore being studied because of their potentially extensive utility.
Heretofore, as macromolecular semiconductors, such polymers as polyacetylene and polyphenylene to which a semiconducting property is imparted by the incorporation of an electron acceptor [Journal of the American Chemical Society, Vol. 100, page 1013 (1978) and Synthetic Metal, Vol. 1, page 307 (1980)] and poly(3-methylthiophene) doped with an anion [Synthetic Metal, Vol. 14, page 279 (1986)] have been known to the art.
These organic semiconductors are generally deficient in stability and heat-resisting property and, therefore, can be used only in limited applications. Since they emit colors only in limited hues when used in displays, their utility in this field is also limited.
Polyacetylenes are highly susceptible to the action of oxygen and instable in the air. They thus have a problem from the standpoint of practical use. Doped polymer of poly(3-methylthiophene) can be easily obtained in the form of a film on the surface of an electrode by the electrolytic polymerization process. The film thus obtained, however, needs further improvement because it does not have a smooth surface and is low in heat-resisting property.
Polythiophene heretofore used as an electrochromic display material can emit only two hues, red in the neutral state and blue when doped with an anion [Japanese Journal of Applied Physics, Vol. 22, page 412 (1983)].